Breast pain while feeding

Asked for Female, 28 Years

My wife is feeding 7 month old daughter. From past one month she is having pain in her left breast and my daughter feeds mostly from left breast. From past two days my wife is having high fever and her left breast is feeling little hard. She had even got blisters on left breast nipples some days back. My daughter feeds at least 6-7 times a day mostly from left breast as my wife has little flat nipples on right side and my baby becomes fussy while feeding from right breast. Is the fever and hard breast interrelated? And what can be done to relive pain.
Thank you